The diagram below represents the NGDF Discovery Metadata in the form of a simplified Unified Modelling Language (UML) Class Diagram. A class diagram is used to describe the static structure of a system in terms of object classes and their relationships. Classes are described in terms of attributes and methods. The attributes define the state of an object and the methods define the behaviour supported by the object. The NGDF guidelines are a data description, they provide no behavioural information; because of this only attributes are shown.

An attribute may be either a single datum or a another class. The metadata structure is thus described in terms of a hierarchy of aggregated classes.

The reader should also note that the diagram has been simplified such that simple classes comprising a single datum but with cardinalities of 0..1, 0..n or 1..n have been subsumed as simple datum values into the higher level class (for example (a) below should strictly be represented as (b)).

This is not strict UML but provides a simpler less cluttered diagram. Likewise, each datum name is followed by its cardinality although this is not UML notation.